Showing results for 
Search instead for 
Did you mean: 

TAPI (TSP) Maximum Simultâneos Connection


I working in a project to integrate a cucm cluster with an Altitude dialer, The dialer is working and we use a Windows 2012 as TSP server.

Agents will use proper cisco hardphones (7821 and some 8945 SIP phones) registred on cucm.

I would be very grateful if some one could help, I need to know how many simultaneous connection a TAPI Server can support.

Becouse I was think to associate all phones to only one application user, and use this same application user on two TSP Server to get High Availability between Altitude environment and cucm cluster.

Is it possible?  I attached the topology.

Really sorry, I was talking wiht PDI Helpdesk but they ask me to open a case on  DevNet.

Thanks a lot for your help

Wagner Fernandes

Cisco Employee

In general, scalability for TAPI is quite good.  You should be able to monitor/control up to 10K max devices from one TAPI instance (user.)

For more details about scalability see the 'Unified CM 8.6.x CTI Improvements.pptx' guide available here:

Cisco TAPI

Cisco Employee

It appears that it is not recommended to use the same user on two TSP servers. This is mentioned in the TAPI Developer guide, under "Multiple Cisco Unified TSPs" :

Ensure that each Cisco Unified TSP is configured with a different username and password that you administer in the Cisco Unified Communications Manager Directory. Configure each user in the Directory, so devices that are associated with each user do not overlap. Each Cisco Unified TSP in the multiple Cisco Unified TSP system does not communicate with the others. Each Cisco Unified TSP in the multiple Cisco Unified TSP system creates a separate CTI connection to the CTI Manager. Multiple Cisco Unified TSPs help in scalability and higher performance.


I think for this particular use-case - 'hot standby' where two app servers 9and TSP instances) want to monitor/control the same set of devices - configuring the same TSP user on each is fine.  For many/most scenarios you do want to make sure to use a separate TSP user to avoid duplicating control, but in this case that's actually the deliberate requirement.


Hello dstaudt,

How are you? First thanks for your help!

I read this doc and I using OVA to 7500 template, I find the CTI factors, I will use only one Line by each device, but I still have a doubt, is these numbers the final scène of cluster??

Because there is another documetation about TAPI instalation  that says : there a limitation on each TAPI of 255 simultaneos automated calls, and this is a limitation of Cisco or legacy wave drivers,    (TAPI Developer Guide) on chapter 4   (page 133)  say that TAPI Server can control only 255 simultaneus calls, it´s a limitation of Cisco Wave Driver

“… Automated Calls -->  The number of Cisco Wave devices determines the number of automated voice lines. (The default value is 5.) The application can open as many CTI ports as the number of Cisco Wave devices that are configured.

For example, if you enter "5," you need to create five CTI port devices in Cisco Unified Communications Manager. If you change this number, you need to remove and then reinstall any Cisco Wave devices which were installed.

A maximum of 255 Wave devices for all installed TSP instances can be configured.

The Wave device limit is specific to MicrosoftTAPI which limits the number of Wave devices per Wave driverto 255.

The Cisco Media Driver does not have this limitation. When you configure 256 or more Wave devices (including Ciscoor other Wave devices), Windows displays the following message when you access the Sounds and Multimedia control panel: "An Error occurred while Windows was working with the Contro lPanel file C:\Winnt\System32\MMSYS.CPL."The current number of possible automated voice lines designates the maximum number of lines that can be simultaneously opened by using both LINEMEDIAMODE_AUTOMATEDVOICE and LINEMEDIAMODE_INTERACTIVEVOICE.If you are not developing a third-party call control application, check the Enumerate only lines that support automated voicecheck box,so the Cisco TSPdetects only linesthat are associatedwith a CTI port device..."

Please what do you think about?

Thanks again!


Hello Smita Upadhya, Thanks for your time,

It´s another doubt, We can install until 10 TSP instances in the same Windows Server, and each TSP needs a diferent application user, it´s a fact,  but if I using different physical Windows Server,  may I use the same application user in both server?

Thanks a lot!



Smita Upadhya

It´s another doubt I know that it´s possible install until 10 TSP instance in the same Windows Server, each TSP Instance needs a different application user on cucm.

The question is, if there are two Windows Servers, with only one instance of TSP for each windows, may I use the same Application User?

Thanks for your Time!!!


Re the 255 wave device limitation:

- This applies only to calls that are terminating on application controlled CTI ports and for which the Cisco TSP wave driver is being used to provide media playback or recording to the caller - not regular phones controlled by the app, which are not limited in this way

- The 255 limit applies only to the 'legacy' TSP wave driver (deprecated on later windows versions.)  The new Cisco TSP 'media driver' does not use the windows sound device infrastructure, and is not subject to the 255 stream limit


Hello dstaudt,

You give me a very good news!!!

It´s true I not using CTI Ports to terminate calls, I using CTI only to Altitude dialer delivery calls to agents that use cisco hardphones!!!!

I going to test this, this week I will post the tests!!!

Thanks a lot for your help!!!!!!

Wagner Fernandes



After reading dstaudt's comment above (nderstand your use case better. Yes, in this case where you are using the 2nd TSP instance as a standby to the 1st (and vice-versa), using the same Application user to control the common set of devices should be fine.



Hello Smita Upadhya,

It´s a good news for me and project that I working!!!!

This week I going to do some tests to validate this environment! I will post the results here

Thanks again for your time and help!

Content for Community-Ad
Cisco Community October 2020 Spotlight Award Winners
This widget could not be displayed.